1. Field of the Invention
The present invention relates to the purification of 2-difluoromethoxy-1,1,1,2-tetrafluoroethane (desflurane), which is a well known inhalation anesthetic.
2. Description of Related Art
U.S. Provisional Application No. 60/643,301 describes a process for the preparation of desflurane by reaction of 2-chloro-2-difluoromethoxy-1,1,1-trifluoroethane (isoflurane) with hydrogen fluoride (HF) over a fixed bed catalysts. This process has a number of advantages in that it is greener than previous processes, highly efficient and adaptable to a continuous process.
Even though this process also yields desflurane of a purity well within the specifications for anesthetic grade desflurane, the product contains a very small amount of 2,2-dichloro-1,1,1-trifluoroethane (R-123) as a by-product. Since R-123 and desflurane have similar boiling points (27° C. ) and 23° C., respectively) it is not easy to separate the R-123 from the desflurane by distillation.
Nevertheless, the ability to remove the R-123 would afford an even purer product. Accordingly, we have endeavored to reduce the R-123 content in the desflurane product.